Private branch exchange

ABSTRACT

A private branch exchange (PBX) capable of transmitting and receiving an E-mail over a network is provided. The PBX includes an interface for communicating with the network, an E-mail server for receiving and storing the E-mail; an extension interface for exchanging a communication signal including an audio signal and control signal with an extension telephone, a database for storing a destination address of an E-mail and an extension number corresponding to the address, an examining unit for examining whether or not an mailing address contained in an E-mail received at the E-mail server from the network is registered in the database, and a controller for sending a notice of the reception of the E-mail the extension telephone of the extension number allocated to the mailing address of the E-mail when the examining unit judges that the mailing address of the E-mail is registered in the database.

FIELD OF THE INVENTION

[0001] The present invention relates to a private branch exchange (PBX)for transmitting and receiving E-mails through a network such as theInternet.

BACKGROUND OF THE INVENTION

[0002] Communication with E-mails through the Internet has rapidly beenspread worldwide. E-mails including common text data and audio data canbe transmitted and received by personal computers including a modem anda Local area network (LAN) interface coupled to a network such as theInternet or the LAN. Other communication apparatuses with display suchas facsimiles coupled to a telephone network can transmit and receiveE-mails through providers.

[0003] Japanese Patent Laid-open Publication 11-205457 discloses acommunication system where E-mails are displayed on a character displayof each extension telephone linked via a computer telephony integration(CTI) interface to a private branch exchange (PBX) without a mailserver. A conventional PBX has a function of transferring an E-mailreceived from the outside to one of extension telephones in addition toa basic function of speaking with other the extension telephones.However, such a conventional PBX may be disadvantageous for users toeasily operate it to exchange E-mails between the extension telephoneand an outline telephone.

SUMMARY OF THE INVENTION

[0004] A private branch exchange (PBX) which allows extension telephonesor dedicated telephones to adequately handle E-mails received through anetwork is provided.

[0005] The PBX includes: an interface for communicating through thenetwork; a mail server for receiving and storing a mail; an extensioninterface for exchanging a communication signal including an audiosignal and control signal with an extension telephone terminal; adatabase for storing a mailing address of a received mail and theextension number of the extension telephone terminal corresponding tothe address; an examining unit for examining whether or not the mailingaddress contained in the received mail received with the mail serverthrough the network is registered in the database; and a controller for,when the mailing address of the mail is registered in the database,informing the extension telephone terminal of the extension numberallocated to the mailing address of the mail.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is a functional block diagram of a private branch exchange(PBX) system including a PBX according to an embodiment of the presentinvention.

[0007]FIG. 2 is a plan view of a dedicated telephone included in the PBXsystem;

[0008]FIG. 3 is a functional block diagram of the dedicated telephone.

[0009] FIGS. 4 to 9 are flowcharts showing an operation of the PBX.

[0010]FIG. 10 is a diagram of a memory structure of a destinationdatabase in a database of the PBX.

[0011]FIG. 11 illustrates a received message displayed on the dedicatedtelephone.

[0012]FIG. 12 illustrates a received E-mail displayed on the dedicatedtelephone.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013]FIG. 1 is a functional block diagram of a private branch exchange(PBX) system according to the present invention. A PBX 100 forconnecting to a network 115 and a public service telephone network(PSTN) 113 includes extension interfaces (I/F) 104 to 107 connectable toextension telephones such as digital telephones or analog keytelephones, a control program memory 108 storing a program forcontrolling the PBX 100, and a central processing unit (CPU) 109, acontroller, for controlling an overall operation of the PBX 100.

[0014] Outline interface (I/F) 110 to 112 are connectable to a digitalor analog switching station over the PSTN 113. An Internet protocolinterface (IP I/F) 114 is connectable to the network 115 such as a localarea network (LAN) or the Internet. An E-mail server 116 transmits andreceives E-mails between the PBX 100 and the network 115 and storing theE-mails transmitted or received. A database 117 stores destinations ofE-mails. A voice mail transceiver 118 transmits and receives voicemails. The transceiver 118 is connected to one of the extension I/Fs forexchanging audio signals with the other external lines and exchangingdigital control signals with the other extensions to record and playback messages or other information addressed to the extensions. Anexamining unit 119 retrieves data from the database. A light-up controlsignal transmitter 120 transmits a signal to light up a message-waitinglamp mounted on each telephone. A text/audio converter 121 converts textdata into audio data and vice versa. A memory 122 stores the convertedtext data and the converted audio data. A type identifying unit 123identifies a type of each telephone. A command detector 124 detectsvarious commands such as key operation data from the telephones.

[0015] A digital telephone 101 operating as the extension telephone suchas a digital key telephone is connected to one of the extension I/Fs forexchanging audio signals and control signals with a digital signal withthe extension I/F. An analog single line telephone 102 is coupled to oneof the extension I/Fs for exchanging call signals and audio signals withthe extension I/F in the form of an analog signal. An analog keytelephone 103 is coupled to one of the extension I/Fs for exchangingaudio signals in the form of an analog signal and exchanging controlsignals in the form of a digital signal with the extension I/F. Acomputer 125 is coupled via an USB port or the like to the digitaltelephone 101 and may be coupled to a network such as the LAN. Acomputer 126 is coupled with a network such as the Internet or LAN.

[0016]FIG. 2 is a plan view of the digital telephone 101 included in thePBX system according to the embodiment. The digital telephone 101 has adisplay 130 such as an LCD and flexible keys 131 capable of beingallocated to particular functions arbitrarily. The flexible keys 131 maybe allocated as an external key (CO key) for displaying a state of theexternal line and connecting to the external line, an extension key (Extkey) for displaying a state of the extension and connecting to theextension line, and a message waiting lamp key for lighting up when avoice mail from the voice mail transceiver 118 or the other extension oran E-mail from the network 115 is received. Control keys 132 are usedfor operating issues displayed on the display 130. Numeral keys 133 areused for entering a command and telephone number.

[0017]FIG. 3 is a functional block diagram of the digital telephoneaccording to the embodiment. A line interface 134 is coupled to thecorresponding extension I/F of the PBX 100 for exchanging audio data andcontrol data in the form of digital signal with the extension I/F. Atype-code storing unit 135 stores the type of the digital telephone 101of the types allocated to the dedicated telephones. A memory 136 is usedfor a telephone number book for the digital telephone and used forcontrolling the operation. A universal serial bus (USB) interface (I/F)137 is connected between the digital telephone 101 and a computer.

[0018] A user, since the digital telephone is connected via the USB I/Fwith the computer 125, can operate the digital telephone 101 from adisplay of the computer 125 and can also receive desired data from thePBX 100. Accordingly, the user can control transmitting and receivingdata on the digital telephone 101 using the computer 125. The commandsignal from the computer 125 to the PBX 100 is transferred from the USBI/F 137 to the CPU 109 controlling the signal through line interface 134and extension I/F 104. In response to the command signal, the CPU 109controls an operation of the digital telephone 101 and supplies, to thecomputer 125, the operation data including the transmitted and receiveddata via the digital telephone 101.

[0019] An audio output unit 138 such as a speaker outputs an audiosignal received from the PBX 100 as sounds. A display 139 such as an LCDdisplays various information. An input unit 140 includes the flexiblekeys, function keys, and numeral keys.

[0020] The computer 125 is coupled via a LAN I/F to the network 115 forexchanging E-mails with the E-mail server of the PBX 100 or other E-mailservers over the network 115.

[0021] An operation of the PBX system having the foregoing arrangementwill be explained below.

[0022]FIG. 4 is a flow chart showing an operation of the PCX 100. AnE-mail from the network 115 received by the PBX 100 is transferred viathe IP interface 114 to the E-mail server 116 in the PBX 100 (Step 1).The server 116 detects information from the E-mail and stores a messageor main data and appendix data including a mailing address asdestination information in a memory in the server 116 (Step 2). It isexamined whether or not the destination address of the E-mail (forexample, Aaa.A.Co.Jp) coincides an address registered in the database117.

[0023] Referring to FIG. 10, the database 117 contains a table of thedestinations set by the user through a device, e.g. a computer connectedto the PBX. The examining unit 119 examines whether the destinationaddress of the E-mail is set or not (Step 3). The table in the database117 shown in FIG. 10 includes extension numbers and group of theextensions in the PBX system and an E-mail address of a computer 126 inthe PBX system to which E-mails are delivered for the destinationaddress. Also, the table may include a group of (attachment destination)addresses to which the attached files of E-mails are delivered.

[0024] When the examining unit 119 recognizes that the destinationaddress of the E-mail is not set in the database 117, the E-mail istransferred to a computer of a predetermined operator (not shown) (Step4). Forwarding the E-mail to the operator may arbitrarily be implementeddepending on the installation of the PBX system and arrangement ofoperators. In case that the computer operated by the operator is linkedto the network 15, a mailing address of the computer is registered inthe database 118 for allowing the E-mails to be received. If theoperator has no computer linked to the network 115 but a switching boardor a dedicated extension telephone, the E-mail may be delivered to them.

[0025] When the examining unit 119 recognizes that the destinationaddress of the E-mail is set in the database 117, the type of theextension telephone connected to the extension I/F for the destinationaddress is identified (Step 5). An extension number is allocated to theextension interface. For example, in case that the database 117 is setas shown in FIG. 10, when the destination address of an E-mail is“Aaa.A.Co.Jp”, a destination “EXT. 102” (extension number “102”),“Grp.2” (extension group “2”), and Baa.Co,Jp (the mailing address of theattached file) are read, and the type of the telephone 102 in the group2 connected to the extension I/F is identified.

[0026] For identifying the type of the telephone, a common public linetelephone or a dedicated telephone, a controller 141 in the extensiontelephone 101 responds by sending a type code stored in the type-codestring unit 135 in response to a type data response command signalreleased from the type identifier 123 instructed by the CPU 109 in thePBX 100. The type of the extension telephone may be identified andstored when the extension telephone is connected to the extension I/F.In this case, the type data response command signal is not necessarywhenever an E-mail is received, and the type of the telephone can beidentified through referring stored results of the examination.

[0027] Then, four types of the telephone to be connected to the PBX 100will be described below.

[0028] The telephone of the first type is a PBX-dedicated key telephonewith a display. The telephone has a display and functional keysincluding a message waiting key, an external line key, an extension key,and a hang-on key. The telephone includes an analog key telephone withfour lines including two communication signal lines and two controlsignal lines, and a digital key telephone with two lines including acommunication signal line and a control signal line. The signals to betransmitted from the PBX to the dedicated telephone include a callsignal for notifying the receiving a call, a display signal for thedisplay, and a type data response demand signal for identifying thetype. The signals to be transmitted from the dedicated telephone 101 tothe PBX carry data about an operation with the function keys, an on-hookand off-hook operations, and the type of the telephone.

[0029] The telephone of the second type is a PBX-dedicated telephonewhich does not have a display. The telephone has a substantiallyidentical function to that of the first type except having no display.

[0030] The telephone of the third type is a common single line telephone102 which does not have a display or a message waiting lamp. Thetelephone of this type, since having a communications line but not asignal line, is disabled to receive control signals from the PBX andtransmit the type code to the PBX.

[0031] The telephone of the fourth type is a telephone equipped with amessage waiting lamp which is substantially identical in the function tothat of the third type.

[0032] The common single line telephone does not have a function forresponding the type data response demand signal transmitted from thePBX. The dedicated telephone can respond to the demand and transmit thetype code allocated to the telephone of the first or second type to thePBX 100. Upon receiving the type code, the type identifier 123 in thePBX 100 examines whether the telephone is the LCD equipped dedicatedtelephone or not. The PBX identifies intermittently the type of thetelephone at predetermined intervals.

[0033] Then, it is examined whether or not a telephone of thedestination is that capable of transmitting an E-mail (Step 6). When thetelephone connected to the extension interface to which the E-mail isdelivered is not the LCD equipped dedicated telephone 101 (of the firsttype) but the dedicated telephone with no display (of the second type),the common telephone (of the type three), or the telephone with themessage waiting lamp 103 (of the fourth type), text data of the E-mailis not displayed. In this embodiment, as far as a message of the E-mailis not converted into texts/audio, the CPU 109 in the PBX 100 maydeliver the E-mail directly to an operator computer without a notice ofthe arrival of a message (i.e. lighting up the LED of the messagewaiting key) (Step 7). This inhibits the message of the E-mail frombeing failed to acquire despite the LED of the message waiting key beingnot lit up due to an incorrect setting of the database or a replacementof the registered telephone of a different type.

[0034] When a destined extension telephone is the dedicated telephone101 having a display such as an LCD, the identifier 123 identifies, onthe basis of the response signal supplied by the extension telephone towhich the E-mail is delivered, that the extension telephone is thededicated telephone 101 having a display. And then, a controllerexamines whether a received E-mail includes an attached file or not(Step 8). If the E-mail contains the attached file and a destinationaddress of an extension telephone having a display to which the file isdelivered, the attached file is delivered (Step 19). If the E-mail doesnot address a telephone which does not have a display, the controllerdelivers the file and other information to the console of the operator(Step 20).

[0035] After the file of information is forwarded at Step 19, if it isrecognized that the E-mail does not include the attached file at Step20, the PBX 100 notifies the extension telephone 101 of the arrival ofthe E-mail addressed to the telephone 101. Simultaneously, thecontroller 109 confirms that the message waiting (MW) lamp key does notlight up (Step 10) and demands to receive a signal for lighting up theMW key (Step 11). When the E-mail includes an attached file of which thedestination is set, the PBX 100 delivers the file to the destination(Step 9). If the destination of the attached file is not set, the fileis forwarded to the computer of the operator.

[0036] The MW key indicates that the dedicated telephone 101 receivesthe response demand from another extension telephone and receives amessage from a voice mail transceiver 118. The MW key, in thisembodiment, is commonly used for notifying the arrival of an E-mail.

[0037] Therefore, when viewing the LED of the MW key being lit up, auser can acknowledge that a text E-mail, a voice mail from the voicemail transceiver, and a message for the response demand from anotherextension telephone are received.

[0038] After the arrival of the E-mail from the PBX 100 has beennotified at Step 11, it is waited that the MW key is pressed down by theuser (Step 12). When the MW key is pressed down, the controllerexamines, in the same manner as of Step 6, whether or not the extensiontelephone to which the E-mail is forwarded is capable of displaying amessage (Step 13). After confirming the telephone is capable, thecontroller transmits a list of the received mails to the extensiontelephone (Step 14).

[0039] Referring to FIG. 11, an example of the list including fivemessages displayed on the LCD screen of the digital telephone 101 willbe explained below. A message 150 “Voice mail 6/11 PM 3:20” means that avoice message is delivered at 3:20 PM on June 11th to the voice mailtransceiver 118. A message 151 “E-mail (Grp1) 6/11 PM 3:25” means thatan E-mail from the network 115 is delivered at 3:25 PM on June 11th tothe extension group 1. A display “Grp” is tagged to a message which isaddressed to one group of extension terminals. For example, whenthirteen extension telephones 101 to 113 are tagged with “Grp 1”, theyall can receive the E-mail. A display “File” means that the E-mailincludes an attached file. The attached file may include an image datafile, a music file, and a specific document data file. In thisembodiment, the digital telephone 101 cannot read a content of E-mail inthe form of text. Therefore, it is set so that the digital telephone 101can not open the attached file. However, the digital telephone 101 maybe set so as to open a specific data file.

[0040] As shown in FIG. 11, as the MW key is pressed by the user, theextension telephone displays a historical list of the E-mails (Step 14).Then, the controller 109 waits for a transmission command from a user byselecting one of the E-mails on the list (step 15). When the user sendthe command, the PBX examines whether the conversion of a selectedmessage into an audio data is preset or not (Step 16). If not, text dataof the message is retrieved by the E-mail server 116 and transmitted tothe extension telephone (Step 17).

[0041] For example, in the case that the user selects the message 152“E-mail 6/11 PM 5:35 (File)”, a command detector 124 of the PBX, uponreceiving a mail transmission command from the extension telephone,extracts data of the E-mail from the E-mail server 116 and delivers itto the telephone. Then, the message of the E-mail from the PBX 100 isdisplayed on the display of the extension telephone as shown in FIG. 12.

[0042] When the E-mail with the attached file has been displayed on thedisplay of the digital telephone 101 as shown in FIG. 12, and the key132 corresponding to letters “FWD” on the LCD display is pressed, a listof the predetermined destinations is displayed. The list may include themailing address and telephone number of the extension telephone equippedwith a display and connected to the PBX 100. This allows the user toselect a desired destination from the list and deliver the E-mail to thedestination. For returning back the E-mail to a sender, the user canselect “RTN” on the display and enter a message in a text file withusing the numeral keys. When the E-mail includes an attached file, themail may be returned back after the attached file is automaticallydeleted.

[0043] If “LOG” on the LCD display is selected, the E-mail is inhibitedfor a predetermined period from being deleted from the database 117 ofthe PBX 100. This allows the user to review the received messagesthrough pressing the message waiting key when all the messages have beenchecked and the key lamp is lit off. The PBX 100 may store a message fora predetermined period even when the “LOG” is not selected.

[0044] The message can be forwarded to a desired extension or addressnumber when the digital telephone 101 receives no call after apredetermined period from the arrival of the preceding message from thePBX 100 in case that the transfer of the message to another extensiontelephone or mail address upon knowing no user available is programmedor when the transfer of the message is set by the user entering thecommand through the keyboard of the telephone 101.

[0045] Referring to FIG. 5, an operation of the controller 109 will beexplained especially in the cases that the extension telephone is notequipped with a display, and that the conversion to audio sounds is setat Step 16. A message of the E-mail is extracted by the controller 109from the E-mail server 116 and converted into audio data by thetext/audio converter 121 (Step 21). Then, the audio data is stored inthe memory 122. Furthermore, the controller 109 determines, on the basisof the result of the type identifier 123, the type of the extensiontelephone to which the audio data is delivered (Step 22). When the typeis a common telephone, the audio data of the message is transferred fromthe memory in the PBX via the extension I/F to the extension telephonewhere the data is output from a speaker as sound (Step 26).

[0046] After the extension telephone is identified with the keytelephone by the type identifier 123, the CPU detects whether or not thetelephone is in an off-hook state (Step S23). When the telephone is inthe off-hook state, the audio data is output from the speaker of theextension telephone as sound (Step 27). If the extension telephone isnot in the off-hook state, the audio data is output from the speakerphone as sound (Step 25) by transmitting a signal for turning on aspeaker phone to the extension telephone (Step 24).

[0047] Referring to FIG. 6, an operation in a case that the message ofthe E-mail is displayed as text data on the telephone at Step 17 will bedescribed below. In the state of displaying the message, the controller109 waits for a command for transfer of the message and a command forhaving a replay received from the extension telephone (Step 31 and Step32). Then, when the extension telephone receives a call or turns to theoff-hook state, the PBX displays a message screen and a call screen onthe display, respectively (Step 33 and Step 34). In case that a messageof a mail is displayed on the display as shown in FIG. 12, when a callis received or made, a screen of the received call or transmitted callis displayed.

[0048] Referring to FIG. 7, an operation in case that the command fortransfer of a message is made at Step 31 will be described below. Thecontroller sends, to the extension telephone, a command of entering dataregarding a destination to which the message is transferred (Step 41),and waits for destination data and a command for starting the transferof the message from the telephone (Step 42). Upon receiving the commandfor starting the transfer, the controller examines whether or not thedestination to which the message is transferred is one of the extensiontelephones (Step 43). When the controller judges that the destination isa communication apparatus such as an external telephone and personalcomputer, the message is transferred via the IP I/F 112 to apredetermined address (Step 44).

[0049] When recognizing at Step 43 that the destination is one of theextension telephones, the controller identifies a type of the telephoneto be addressed (Step 45). The controller, then, examines whether or notthe extension telephone of the identified type is capable of receivingan E-mail (Step 46). If the telephone is not capable, the controllernotifies the telephone of disability of a transfer of the mail (Step47).

[0050] When recognizing at Step 46 that the telephone is capable ofreceiving the mail, the controller examines whether or not the mail tobe transferred includes an attached file (Step 48). When the mailincludes an attached file, and the extension telephone to which the mailis delivered has a destination address for the attached file, theattached file is transferred to the destination extension (Step 51). Ifthe extension telephone does not have the destination address for theattached file, the controller displays a notice of disability of atransfer of the attached file on the display of the extension telephonewhich requests the transfer (Step 50).

[0051] When it is recognized at Step 48 that the mail does not includean attached file, or after the attached file is transferred with theoperation at Step 50 and Step 51, the controller examines whether or notthe MW key on the extension telephone to which the mail is forwardedremains lit up (Step 52). When detecting that the MW key is not lit up,the controller transmits a command signal for lighting up the MW key(Step 53). When detecting, at Step 53 or Step 52, that the MW keyremains lit up, the controller detects a signal indicating that the userpresses the MW key (Step 54). The controller then examines whether ornot the extension telephone is capable of displaying the message (Step54). When the telephone is capable, a list of the received mails istransmitted to the telephone (Step 56).

[0052] Then, the controller waits for a command of sending a mailselected by the user (Step 57). When receiving the command, thecontroller examines whether or not the conversion to audio data is set(Step 58). If not, the text message of the mail is transferred to theextension telephone (Step 59).

[0053] Referring to FIG. 8, an operation in a case that the request forreply is received at Step 32 will be explained below. When receiving therequest for reply at Step 32, the controller instructs to input a replymessage (Step 61). Then, the user inputs the reply message (Step 63).Further, the controller sends the extension telephone data of a screento request to input a destination of the reply to instruct to input thedestination, and waits for an input by the user (Step 64). Thecontroller waits for a command of starting the reply from the user (Step63).

[0054] When receiving the command of starting the reply entered throughthe telephone by the user, the controller examines whether or not thedestination to which the replay is addressed is one of the extensiontelephones (Step 64). If the destination is a communication apparatussuch as an external telephone and personal computer, the reply messageis transferred via the IP I/F to the external destination (Step 65).When recognizing that the destination is one of the extensiontelephones, the controller identifies the type of the destinationtelephone (Step 66) and examines whether or not the destinationtelephone is capable of receiving the mail message (Step 67).

[0055] When recognizing that the mail message is not accepted, thecontroller notifies the telephone of disability of transfer of themessage (Step 76). When recognizing that the destination telephone iscapable of receiving the mail message, the controller examines whetheror not the MW key of the destination telephone remains lit up (Step 68).If not, the controller transmits a signal for lighting up the MW key(Step 69).

[0056] While the MW key of the destination telephone remains lit up, thecontroller examines whether the MW key is pressed down or not (Step 70).

[0057] When detecting that the MW key is pressed down, the controllerexamines whether the destination telephone has a display or not (Step71). When it has a display, the controller sends a list of receivedmails to destination telephone (Step 72). Then, the controller waits fora command of transmitting the mail message from the user (Step 73). Whenreceiving the command, the controller detects whether or not theconversion into audio data is set (Step 74). If it is not set, thecontroller sends a text data of the message to the destination telephone(Step 75).

[0058] Another method of controlling the private branch exchange (PBX)according to the embodiment will be described.

[0059]FIG. 9 is a flowchart showing an operation of the PBX 100 in themethod. An E-mail addressed to one of the telephones connected to thePBX 100 is received via an Internet protocol interface (IP I/F) 114 byan E-mail server 116 in the PBX 100 (Step 81). The server 116 stores amain message and appendix data such as a mailing address (a destinationaddress) of the E-mail (Step 82). The examining unit 119 then examineswhether or not the destination address of the received E-mail (forexample, Aaa.A.Co.Jp) is registered in a database 117. The database 117contains a table of the destination addresses set by the user as shownin FIG. 10. An address examining unit examines whether or not thedestination address of the received E-mail is listed in the table (Step83).

[0060] As shown in FIG. 10, the table in the database 117 may include anextension number, group of extensions in the PBX system, and E-mailaddress of a computer 126 corresponding to the destination address towhich an E-mail is delivered. The table may further include a group ofaddresses or attached file destinations to which the attached files ofE-mails are forwarded.

[0061] When the address examining unit 119 recognizes that thedestination address of the E-mail is not set in the database 117, theE-mail is transferred to a computer of an operator (not shown) (Step84).

[0062] When it is judged at Step 85 that a destination address of theE-mail and the extension terminal to which the E-mail is forwarded areset in the database 117, and when the extension terminal is allocated tothe destination address, the E-mail including an attached file aretransferred to a communication device such as a personal computer (Step86). The relationship between the extension terminals and the addressesis shown in FIG. 13. For example, the extension number “102” isallocated to an address “Aaa.B.Co.Jp”. The controller turns on the MWlamp of the extension telephone and delivers the E-mail addressed to“Aaa.B.Co.Jp”.

[0063] Then, a type of the telephone is confirmed from the address ofthe telephone to which the E-mail is delivered (Step 87). When the typeof the telephone is capable of receiving the E-mail, the controllerinstructs to delete the attached file of the E-mail from the E-mailserver 116 (Step 89).

[0064] The controller examines whether the MW key of the destinationtelephone remains lit up or not (Step 90). If not, the controller turnon the MW lamp. That is, the controller 109 sends light-up message datato the extension telephone through the extension I/F. The controllerexamines whether or not the telephone receives the E-mail (Step 91).When the telephone does not receive the E-mail, the controller examines,from data sent from the E-mail server, whether or not a mail indicatingthat the mail delivered at Step 85 is received from a devicecorresponding to the destination address (Step 92). The devicecorresponding to the destination address has a mailing program installedto send, to the PBX, an E-mail indicating to receive an E-mail when acontent of an E-mail sent from the PBX. When the mail is received, thecontroller examines whether the telephone has another messages than themail or not (i.e., whether the telephone has a message to be confirmedor not) (Step 93). If the telephone does not have a message to beconfirmed, the controller turns off an LED of the MW key of thetelephone (Step 94).

[0065] The LED of the MW key is turned on when the telephone has amessage (an E-mail or voice mail) to be confirmed, and turns off whenthe controller judges that all message to be confirmed is confirmed. ThePBX transfers an E-mail received at the E-mail server to the extensionterminal addressed by the E-mail and a computer corresponding to theextension terminal. When the user opens the E-mail at the computer towhich the E-mail is addressed before the E-mail is confirmed at theextension telephone, the computer send the E-mail server a notice mailof receiving the E-mail. The MW lamp of the extension telephone isturned off by the PBX in response to the notice mail. Therefore, theuser does not have to confirm the E-mail on the extension telephoneagain even if the user has a dedicated telephone and a computer on adesk. Further, the E-mail can be stored and managed with the computer.

[0066] Many modifications and variations of the present invention arepossible in the light of the above techniques. It is therefore to beunderstood that within the scope of the invention, the invention may bepracticed otherwise than as specifically described.

What is claimed is:
 1. A private branch exchange capable of transmittingand receiving a mail through a network and coupling with extensiontelephones, said private branch exchange comprising: an interface forcommunicating with said network; a mail server for receiving and storingthe mail; an extension interface for exchanging a communication signalincluding an audio signal and control signal with said extensiontelephones; a database for storing an extension number of said extensiontelephone and a mailing address corresponding to the extension number;examining means for detecting whether or not a mailing address containedin the received mail corresponds to a mailing address stored in saiddatabase; and controlling means operable to notify said extensiontelephone having an extension number corresponding to the mailingaddress when said examining means detects that the mailing addresscontained in the received mail corresponds to the mailing address storedin said database.
 2. A private branch exchange according to claim 1,wherein said extension telephone includes mail reception notifyingmeans, and wherein said controlling means is operable to notify saidextension telephone of receiving the received mail by transmitting asignal for activating said mail reception notifying means.
 3. A privatebranch exchange according to claim 1, wherein said controlling means isoperable to transmit a predetermined signal to said extension telephone,and notify said extension telephone having the extension numbercorresponding to the mailing address contained in the mail according toa response to the predetermined signal from said extension telephone. 4.A private branch exchange capable of transmitting and receiving anE-mail through a network and communicating with a plurality of extensionterminals, said private branch exchange comprising: an Internet protocol(IP) interface for communicating with said network; an E-mail server forreceiving and storing the E-mail; a plurality of extension interfacesfor exchanging communication signals each including an audio signal andcontrol signal with said extension terminals; a destination database forstoring destination addresses of an E-mail and destination extensionnumbers of extension terminals corresponding to the destinationaddresses; and controlling means operable to: when a message isdelivered from one of said extension terminals to other of saidextension terminals, notify said other of said extension terminals ofreceiving the message; when said E-mail server receives an E-mailthrough said network, detect whether or not a destination addresscontained in the received E-mail is stored in said destination database;and when detecting that the destination address contained in thereceived E-mail is stored in said destination database, notify said anextension terminal of said extension terminals, said extension terminalhaving an extension number corresponding to the destination address. 5.A private branch exchange according to claim 4, wherein at least one ofsaid extension interfaces is capable of coupling with voice mailreceiving means, and wherein, when a message is delivered from saidvoice mail receiving means to one of said extension terminals, saidcontrolling means is operable to notify said one of said extensionterminals of receiving of the message.
 6. A private branch exchangeaccording to claim 4, wherein each said extension terminals includesmail reception notifying means, and wherein said controlling means isoperable to notify said extension terminal having the extension numbercorresponding to the destination address by transmitting a signal foractivating said mail reception notifying means.
 7. A private branchexchange according to claim 4, wherein said controlling means isoperable to transmit a predetermined signal to said extension terminals,and to notify said extension terminal having the extension numbercorresponding to the destination address contained in the receivedE-mail in response to a response to the predetermined signal from saidextension terminals,
 8. A private branch exchange capable oftransmitting and receiving an E-mail through a network and communicatingwith a plurality of telephones, said private branch exchange comprising:an interface for communicating with said network; an E-mail server forreceiving and storing the E-mail; a plurality of extension interfacesfor exchanging a communication signal including an audio signal and acontrol signal with said telephones; a database for storing extensionnumbers of said telephones and destination addresses for the E-mailcorresponding to the extension numbers; converting means for convertingtext data in the an E-mail into audio data and vice versa; andcontrolling means operable to: when an E-mail is received at said E-mailserver from said network, and when a destination address contained inthe received E-mail is stored in said database, notify a first telephoneof said telephones, said first telephone having an extension numbercorresponding to said destination address, instruct said convertingmeans to convert text data of the received E-mail into first audio datain response to a command transferred from said first telephone, andtransferring the first audio data to other telephone of said telephones,said other telephone being determined by the first telephone.
 9. Aprivate branch exchange according to claim 8, wherein each saidtelephones includes mail reception notifying means, and wherein saidcontrolling means is operable to notify said telephones of receiving thereceived E-mail by transmitting a signal for activating said mailreception notifying means.
 10. A private branch exchange according toclaim 8, wherein said controlling means transmits a specific signal tosaid telephone terminals, and notify said first telephone based on aresponse to the specific signal from said telephones.
 11. A privatebranch exchange capable of transmitting and receiving a mail over anetwork and coupling with an extension telephone, said private branchexchange comprising: an interface for communicating with said network; amail server for receiving and storing the mail; an extension interfacefor exchanging a communication signal including an audio signal andcontrol signal with said extension telephone; a first database forstoring an extension number of said extension telephone and a receivablemailing address corresponding to the extension number; a second databasefor storing an extension number of said extension telephone and adestination address corresponding to the extension number; examiningmeans for detecting whether or not a mailing address contained in thereceived mail corresponds with the receivable mailing address stored insaid database; and controlling means operable to, when said examiningmeans judges that the mailing address contain in the received mailcorresponds with the receivable mailing address stored in said firstdatabase, notify an extension telephone having an extension numbercorresponding to the mailing address, and transfer the received mail toan destination address corresponding to the extension number store insaid second extension number.
 12. A private branch exchange according toclaim 11, wherein said extension telephone includes mail receptionnotifying means, and wherein said controlling means is operable tonotify said extension telephone of receiving the received mail bytransmitting a signal for activating said mail reception notifyingmeans.
 13. A private branch exchange according to claim 11, wherein saidcontrolling means is operable to transmit a predetermined signal to saidextension telephone, and notify said extension telephone having theextension number corresponding to the mailing address contained in thereceived mail on the basis of a response to the predetermined signalfrom said extension telephone.
 14. A private branch exchange accordingto claim 11, wherein, in the case that, after transmitting a mail to thedestination address, said controlling means receives a mail indicating adevice having the destination address receives the transmitted mail,said controlling means is operable to cancel to notify an extensiontelephone having an extension number corresponding a mail addresscontained in the received transmitted mail.